Square’s popular free invoicing software is becoming the company’s next big subscription service. The company is poised to announce a paid subscription offering called Invoices Plus, which will offer sellers a set of advanced features, including some that had previously been available with the free service. The service itself had been quietly introduced to individual sellers, but has not yet been publicly announced. the new subscription will include a series of features that were released in the past year as part of a limited trial. This includes multi-package estimates, custom invoice templates and custom invoice fields. These will now become a part of Invoices Plus, as will two other features: the ability to automatically convert accepted estimates to invoices and the ability to build milestone-based schedules (three-plus installment invoices). Square will introduce a “trial” button next to these features in the Square Invoices software to alert customers to the upcoming capabilities. Square’s free invoicing software will not go away. Sellers will be able to send unlimited invoices for free, as well as estimates and contracts, with the free plan. Free users will also be able to use invoice tracking, reminders and reporting tools.